none
VM connected at 10MBps RRS feed

  • Question

  • Hello,

    I have a two node hyper-v host cluster and the Ethernet cables for the virtual networks are connected to 1GBps switch ports. Due to performance issues with a VM our network group ran a test to see what speed a virtual machine connected to the switch at and determined that it was connected at 10MBps. Looking at the network adapter on the VM it shows as being connected at 10GBps. We mapped a drive to the server and copied a file. We were seeing about 1MBps file transfer speeds. 

    Is there a way on the server to determine the actual speed at which a VM connects or hard code the network adapter to connect at a certain speed? 


    Pat

    Thursday, March 17, 2016 1:07 AM

Answers

  • The Virtual Switch is 10Gb.  That is what a VM will see.

    Your physical NIC is only 1Gb.  You cannot overcome that with any magic.

    So, all networking rules applied, the smallest soda straw is your limiting factor.  No different than the slowest WAN pipe.

    And no, you cannot limit the speed of a virtual NIC.

    But you can set limits per VM:

    https://technet.microsoft.com/en-us/library/hh831679.aspx


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.

    Thursday, March 17, 2016 2:30 PM
    Moderator

All replies

  • Hi Pat,

    >>Is there a way on the server to determine the actual speed at which a VM connects or hard code the network adapter to connect at a certain speed? 

    As far as I know, the VM only has virtual NIC, there is no built-in method to get the speed.

    File copy is not a recommended method to test the network speed. I suppose a network speed test application could give the accurate result.

    Besides, I have seen posts about the network speed inside VM. A physical NIC of higher speed may improve the speed inside VM. You could have a try.

    Best Regards,

    Leo


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.

    Thursday, March 17, 2016 6:43 AM
    Moderator
  • The Virtual Switch is 10Gb.  That is what a VM will see.

    Your physical NIC is only 1Gb.  You cannot overcome that with any magic.

    So, all networking rules applied, the smallest soda straw is your limiting factor.  No different than the slowest WAN pipe.

    And no, you cannot limit the speed of a virtual NIC.

    But you can set limits per VM:

    https://technet.microsoft.com/en-us/library/hh831679.aspx


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.

    Thursday, March 17, 2016 2:30 PM
    Moderator
  • I wanted to update everyone on what I found. To make a long story short, I ended up trying three different NIC ports on the server and 3 different switch ports. Every time the NIC would auto negotiate at 1Gbps but then drop to 100Mbps at random times. It could've been stable at 1Gbps for 5  minutes or 8 hours and then would drop to 100Mbps. From where my server is and the switch we have to go through 4 different patch panels. I decided to try and use one long network cable to connect the server to the switch and bypass all the network cables and patch panels in between. After connecting this long network cable, the NIC remained stable for 24 hours when I decided to unplug it and start troubleshooting the network cables. As it turned out we had a bad network cable in our path. After replacing that network cable we've had a stable connection for over a week now. What I don't fully understand is we tested this whole network path with a cable tester and it passed. Maybe it passed but passed at 100Mbps? I don't know. Our tester does not tell us what the speed is but I wanted to update this thread for anyone else that might experience the same symptoms. Our network cables were all pre-made and come with test sheets.

    Pat

    Tuesday, April 5, 2016 12:47 PM